A previously well 28-year-old male is brought to the Emergency Department following an accident in the garden. He was on a ladder pruning a tree when he touched an overhead power line and was electrocuted. He was thrown to the ground, unconscious and had bystander CPR. Paramedics arrived after 10 minutes, and intubated and ventilated the patient who had return of spontaneous circulation and a Glasgow Coma Scale of 5 at the scene.

a) List the major issues that you would consider in the initial management of this patient. (40% marks)

b) After four days, he develops anuric acute kidney injury (AKI). Describe how you will assess the factors contributing to the AKI. (60% marks)

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College answer                                                                                                                                       

a)

The potential issues the that need to be considered in this patient include

  • Electrocution
  • Trauma from the fall
  • Hypoxic-ischaemic brain injury
  • Aspiration
  1. Electrocution
    • Myocardial damage/Unstable rhythm
    • External burns
    • Rhabdomyolysis/ internal tissue burn / compartment syndrome.
    • Electrolyte abnormalities e.g. hyperkalaemia
    • Traumatic injuries as below
    • Hypovolaemia due to fluid extravasation
    • Neurological damage –central and peripheral, including autonomic neuropathy
  1. Hypoxic-Ischaemic Brain injury
  1. Trauma from the fall
    • Head and or spine injury
    • Blood loss
    • Abdominal injury
    • Rib fractures
    • Long bone/ pelvic injury
  1. Aspiration 
    • Pneumonitis
    • Foreign body aspiration

b)                                                                                                                                             

The assessment of factors contributing to AKI in this setting

Pre-renal causes

  • Most likely o Ongoing/ new hypovolaemia
    • Low cardiac output secondary to myocardial injury o Renal artery/vein injury from trauma
  • Assess volume status
  • History, examination, monitoring, investigations
  • Check Hb
  • * echocardiography
  • Urinary fractional sodium excretion

Renal causes

  • Most likely o Rhabdomyolysis o Other nephrotoxin o Abdominal compartment syndrome
    • Drug reaction -> interstitial nephritis
  • Examination for ongoing compartment syndrome, check CK
  • Assess medications and cease any nephrotoxins (NSAIDS, gentamicin, vancomycin)
  • Examination of abdomen, measure intra-abdominal compartment pressure, consider renal ultrasound with duplex if retroperitoneal haematoma
  • Urinary microscopy to look for casts, assess medications for potential causes (penicillins, cephalosporins, pantoprazole)

Post renal causes

  • Most likely IDC obstructed, or clot in renal pelvis, pelvis causing ureteric obstruction
  • Ensure IDC not blocked o Flush catheter, bladder ultrasound o Renal ultrasound to exclude obstruction

Discussion

Major issues in the management of the patient:

  • Airway:  assess the ETT tip position: he was intubated in the field, and the ETT position may be sub-optimal
  • Respiratory management: assess the efficacy of mechanical ventilation; the patient may have developed pulmonary oedema. A CXR would be in order.  
  • Cardiovascular management: ECG to assess the effect the current had on the conduction system, and the presence of any ischaemic changes. Ensure pacing is available. The patient will likely go on to develop a global reperfusion injury, and a vasodilated state should be expected.
  • Transthoracic echo / inotropes: cardiac function needs to be assessed; depressed contractility may be expected
  • Neurological management: this comatose survivor of cardiac arrest may also have hit his head falling off that ladder.
    A CT brain would be in order to exclude intracranial haemorrhage. Once that is done, he may be cooled in by some sort of a therapetic temperature management protocol, down to 36° for 24 hours.
  • C-spine: the patient had a fall; C-spine fracture needs to be excluded.
  • Electrolyte management: there is a high likelihood of some potassium and phosphate elevation due to muscle breakdown (thus, assess with blood biochemistry). Serum calcium may be low, and may require replacement
  • Fluid management: burns and damaged muscle will attract fluid and result in evaporative/exudative loss in the case of the former and third-spacing in the case of the latter. Physical examination and BP monitoring will reveal this. Fluid 
  • Musculoskeletal trauma: the fall and violent spasmodic muscle contraction may have given rise to bone fractures. Arcing of high voltage current may have resulted in burns. It would be important to assess these by a whole-body survey. 
  • CT of the extremities: myonecrosis may be hidden; deep burns may have no external manifestations
  • Rhabdomyolysis: myonecrosis may occur; a CK level will reveal this. The patient should receive a sufficient amount of fluid to promote diuresis, as well as an alkalinising agent such as sodium bicarbonate.
     

Part b) asks about the assessment of renal failure in this patient. That's got to be a 6-mark (60%) answer, so it can't just be "send a CK and urinary myoglobin". Sure, the high voltage injury is likely the cause of some deep myonecrosis and this has probably put the patient into a rhabdomyolysis-induced ATN. However that is not the only possibility. Because the patient is complex and may have multiple problems by Day 4, there may be numerous differentials for this AKI. For instance, the 30 minutes of 'down-time" during the cardiac arrest may have given rise to a global hypoxic-ischaemic reperfusion syndrome, and the ATN might be due to that. Or the burns resulting from the electrocution resulted in a prothrombotic state and the patient has developed renal vein thrombosis. Or the IDC is blocked. In short, one would need to deploy a lightly electric-flavoured version of the usual workup for acute kidney injury.

That would look a little like this:

  • Rule out mechanical obstruction
    • Explore the IDC (is it blocked?)
    • Perform a renal tract ultrasound
  • Exclude obvious causes of pre-renal failure
    • Exclude abdominal compartment syndrome due to intraabdominal burns
    • Exc
    • Renal vascular disease (one may wish to perform renal doppler studies to exclude renal artery stenosis or renal vein thrombosis)
  • Examine the urinary sediment
    • Hyaline casts are not associated with anything specific
    • Fatty and waxy casts are suggestive of long-standing renal disease, whatever its cause.
    • Muddy brown (coarse granular) casts and tubular epithelial casts are associated with ATN
    • Red blood cell casts indicate glomerular disease
    • Shredded-looking RBC fragments also indicate glomerular disease
    • Intact-looking red cells suggest some source of bleeding inside the urinary tract, eg. calculi trauma, malignancy, or the haemorrhagic cystitis of cyclophosphamide therapy.
    • Eosinophils in the urine, especially when they comprise in excess of 5% of the total urinary WCCs, may suggest acute interstitial nephritis
    • White cells in excess, and white cell casts specifically, suggest pyelonephritis
    • Pigmented casts may suggest myoglobin as the cause of ATN
    • Urinary myoglobin levels confirm rhabdomyolysis
    • Urinary crystals suggest some sort of crystalline nephropathy (they might be urate, oxalate, sulfonamides, etc)
  • When all else fails
    • A renal biopsy may yield diagnostic information, provided one manages to biopsy something relevant. Potentially, one's sample could be full of uselessly necrotic parenchyma, which all looks the same (therefore there will still be no diagnosis, and now one's patient has a hole in their kidney).

References